


'Sweet' Dreams Are Made of These

by DragonsBloodJasper



Category: Undertale (Video Game)
Genre: Alternate Universe - Dreamtale (Undertale), Dubious Consent, F/M, In a way, Knotting, Many tentacles, Nightmare!Sans - Freeform, Reader is a Sans, Reader is named, Skeleton Reader, Tentacles, first post on ao3, may write more chapters, monster reader, reader can fend for herself, reader has muscles, reader is pretty much an oc of mine?, reader is strong
Language: English
Status: Completed
Published: 2019-11-18
Updated: 2019-11-18
Packaged: 2021-02-12 20:09:22
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,679
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21482128
Author URL: https://archiveofourown.org/users/DragonsBloodJasper/pseuds/DragonsBloodJasper
Summary: You are in no way a push over, the nature of your universe made sure of that, but HE seemed to love pushing your buttons and driving you crazy to the point you actually try to harm him. But today is different, HE didn't have that infuriating smile on his stupid face nor did he carry that amused but malicious aura.
Relationships: Nightmare sans/reader, Sans (Undertale)/Reader
Comments: 16
Kudos: 203





	'Sweet' Dreams Are Made of These

**Author's Note:**

> So this is a self indulgent story but I wanted to share it?  
This is the reader- https://twitter.com/RustedKaibutsu/status/1183554503129423872 art is by me! (her name is Clarity btw ouo)

Your socket twitched in irritation as you felt that tell-tale shiver of dread rattle down your spine, a feeling that you have come to know very well over the past few decades he has been tormenting you.

Nightmare was a alternate you have regretted meeting ever since you've met that strange group of Sanses, you think they called themselves 'The Star Sanses', and ever since then he has been a pain in your coccyx. You were in no ways a weak Sans, you didn't have the handicap of having one HP like the majority of them did thankfully, if anything you were pretty sturdy coming from a universe like yours. 

You come from a universe that required survival -you couldn't afford to be weak or else you'd be nothing but dust within hours- so you were quite the difficult opponent to take down. You weren't too concerned when the tar-covered king of negativity first appeared, thinking that this was just a Sans passing through your universe just like the three that had just visited, if anything you didn't care to much about anything concerning other universes. You were content with your universe and didn't want to meddle into the drama with other AUs, you were still a Sans after all, so you decided to just lazily go on with your day as if nothing had happened, but Nightmare just had to ruin your peaceful life. The self-proclaimed 'king' had came, following his brother's trail -Dream, you think that's his name was- in hopes of finally destroying his lighter twin. 

You had been amused at first, smiling that typical Sans smile, and of course decided to mess with the angry ball of hate. Throwing out a few puns here and there about his failure and hostility, dealing with the anomaly had been proven helpful as you easily dodged the wicked sharp tentacles that had been aimed to kill you. Back then you had taken him as a joke, thinking that you wouldn't see him again after his departure. Oh how wrong you had been. Ever since then he had appeared time and time again to try to dust you on the spot for 'disrespecting the king', he had almost succeeded a few times before that cursed group intervened. You had come to dislike all of them relatively fast, Nightmare for his daily attempts to off you, and the Star Sanses for their thought that you needed protection. It irritated you greatly at their constant hovering -as if you were a defenseless baby bones who couldn't protect herself- you blamed it all on the god dammed walking tar pit.

But then the daily murder attempts stopped. You had hopped, prayed even, that the lot of them had finally decided to let you be and go on with their own business. But all your hope vanished once Nightmare had appeared yet again, this time carrying a different aura rather than his murderous one. It made you weary and cautious at the sudden change, you half expected him to try and catch you off guard. But the attempts at dusting you never reoccurred, instead he was more amused than angry at your obvious dislike for him. Even more so when you voiced your dislike for his brother's group as well.

His murder attempts soon morphed into dodging your murder attempts as he picked at your nerves, throwing insults and cruel teasings as you tried your best to ignore him. Thinking that he'd give up if you showed no reaction. To be honest you never though you'd hate someone more than the human, but Nightmare had quickly scaled that list in under a single decade.

And now you are here, smile strained into a scowl as you glared hatefully in the direction you knew he'd appear. You knew this game well enough to sense his presence before he manifested from the dammed shadows he always did. Your sockets squinted in slight confusion as a new scent flooded your senses, it wasn't the usual rancid smell of dust and negativity that Nightmare always emitted, it was -in a way- sickeningly sweet and turned the magic in your stomach as it quickly spread through the area, your skull spun slightly at the overwhelming scent.

Growling loudly you shook off the haze that made your head spin in a dizzying array "What do you want," you hissed out in a deep but feminine voice. Your scowl only deepened as you heard the husky chuckle coming from the taller skeleton "Now that's now way to talk to your king," he said in a deeper than usual tone, his voice slurring slightly as he leered over you. 

"And I've told you countless times before, fuck off," you said with a threatening growl, noticing the change in the way he carried himself. Nightmare was usually hunched over in that classic 'Sans' fashion that all his alternates, even you, had. Today he was standing with his back straight, making himself noticeably taller than yourself, his ever-present grin was sharper and more predatory than before as he peered at you with his malicious, glowing teal eyelight. You couldn't help but tense, the change unnerved you greatly.

His response to your words was a deep growl of a chuckle, eye squinting in dark humor as he took a threatening step towards you "Maybe you just need to learn who's in charge here" he growled back. Your eyes widened in alarm as you instinctively dodged the onslaught of dark tendrils that had been aimed towards you, this was new for you. Nightmare had never attacked like this, always morphing his tentacles in various sharp and deadly weapons that could easily cut you down with a single wrong step from your side. This wasn't that, his normally deadly weapons of choice weren't sharp and deadly but blunt and dull. Each tendril that you dodged only seemed to be trying to grab you and render you immobile, a few even shaping into large clawed hands that tried to grab at your neck, legs, and arms.

Sweat dripped down your skull in nervousness, your legs shook as you were forced to dodge the relentless waves of attacks, failing to notice that the source of the attacks had melted away into nothing but shadows. He had made sure you were focused on his attacks rather than himself -a fatal mistake as he reformed behind you- causing you to crash against the taller's broad chest. Nightmare had wasted no time to pin you, arms wrapping around your chest to pin you painfully close against his ribs. You hissed and spat as you writhed in his vice-like grip, magic straining to push him away as you tried to tug your arms free from your sides.

A loud hiss from the side of your skull made you freeze, Nightmare's grip only tightened as he bared his teeth against your covered neck "I wouldn't struggle anymore if I were you," he hissed out in a warning "It would be a shame if I were to lose control, then you wouldn't enjoy this very much" he rasped as his tar-covered tentacles loosely snaked around you both. Your sockets widened in shock, it made sense to you now, the change in posture, his voice, the dizzying aroma, Nightmare had gone into heat!

A loud raspy gasp was pulled from your mouth as the taller began grinding into your pelvis, you could feel the obvious bulge in his shorts as he began practically dry humping you. Your gasp made him chuckle deeply "you feel that," he asked as his grinding became much harsher and he began to pant "that's all for you, aren't you lucky?"

Your only response was a muffled moan as you tried to free yourself once more, your struggles were futile as the king of negativity's tentacles wrapped themselves around your knees and ankles, making your legs spread wide as Nightmare practically sat you in his lap as he decided to seat himself on the ground "That's it" he purred darkly as he jerked his hips harshly against yours "Just give in" he coaxed in a false gentleness, one hand wandering down to harshly rub your pelvic inlet causing you to whimper softly. You tried to prevent your magic from taking form, the pressure forming inside your chest and pelvis increasing the more you resist.

A lazy grin spread on Nightmare's face, morbidly amused at your resistance and the discomfort it was causing "Perhaps you need a little help" he states in a sickeningly sweet tone. His hand ground harder, claws digging into your clothes to scrape against your sensitive bones causing you to wince, it was causing more pain than pleasure. "Form something now," he commanded to the side of your head "Then all the pain will go away." with this said the tendrils not holding your legs sneaked inside your clothes, cold and dripping they caressed your spine almost teasingly. You couldn't take it anymore as your magic finally formed, molding into a slim shape with decent sized breasts and a dripping entrance.

You could hear Nightmare's pleased growl as his hips jerked up in anticipation, making his bulge grind roughly into your formed magic and forcing a shocked yelp from you. Nightmare made quick work of your clothes, the baggy, turtlenecked jumper shredding into bits as the tentacles inside flexed and strained the threads, you were left bare within moments from the male's eagerness to rid of the barrier between you and him. You didn't expect to be forced to turn around speared onto an eagerly awaiting tentacle, the sudden stretch and fullness made your sockets widen and tear up. It was too much too fast, the tentacle reaching so far that it made your stomach bulge out as it forced itself as deep as it could. A loud cry of pain escaped you as your body locked up, legs and hips tensing to prevent your body from moving. 

Nightmare groaned loudly as your magic squeezed him tightly, sending bolts of pleasure up his spine and into his pelvis. Panting he rested his skull on your vertebrate, gnashing his teeth together as he reigned back control over his body. He was evil, yes, but he wanted his chosen 'mate' to enjoy their coupling as well. A deep purr vibrated through his chest as he listened to your pained whimpers, your own skull buried against his neck as your magic adjusted to his tentacle. A clawed hand raised to comb through the mass of 'hair-like' tentacles growing from the back of your skull, they had unwound from their usual 'ponytail' fashion due to their owner's pain.

The king of negativity 'shhhhh'ed your whimpers softly as he combed through your 'hair', waiting with unnerving patients as your magic began swelling and adjusting to his intrusion. The tentacle writhing every now and again to test the waters until you finally let out an unwilling moan, the movement finally causing a jolt of pure pleasure through you "Hehehe, finally ready?" he asked with a smirk, nuzzling your neck as he forced your hip to rock and stimulate the tentacle inside you. 

"Ah-ahgn" you couldn't help but moan, your arms instinctively rising to clutch at the back of Nightmare's hoodie as your hips were moved, your magic pulsed around him before clamping down tightly. This made the male freeze and hiss at the unexpected tightness, it didn't take him long to know that you had cummed, his smirk widened into a sick grin with the knowledge that he had been the only one to ever mate with you. He had ruined you first and no one else would ever have the chance to. With this thought he began to thrust his tendril in and out of you roughly, the sudden stimulation making you cry out as your walls were painfully overstimulated. Blue tears leaked from your sockets as you were quickly built up into another orgasm, causing you to sob "t-t-too much!" you protested as you clenched your thighs to try and halt the tentacle's movement.

Nightmare chuckled lowly "but your doing so good," he purred, gripping your body tightly as he continued with his relentless thrusting "you already came for me twice, how many can I pull out of you with just one?" he pondered, cruelly curling the tentacle inside you to rip out another scream of pleasure "your screams are just too good to resist" he hummed into your neck, his cheeks had begun to flush a soft teal color as his thrusting got harsher until he finally allowed himself to release with a soft groan. You gasped as the tentacle inside you soaked your insides with a thick, black fluid, it made you shiver as it clung and soaked into your magic, you groaned softly as it slipped out of you with ease allowing the fluid inside to begin to trickle out. Nightmare 'tsked' at this "already wasting it huh?" he asked with a wicked grin, making you shiver in slight fear, "I guess we'll just have to fix that" he stated as another tentacle moved to take the other's place causing you to gasp as it speared itself into your stomach "we have a few more to go before the main course" he said with a purr as he began thrusting the new tentacle.

This went on for hours, each tentacle pulling orgasm after orgasm out of you before filling your insides with their owner's magic only for it to be replaced soon after. The cycle went on and on until you couldn't think of anything but the pleasure and the numbness that started to spread through your pelvis and legs, you didn't have the strength to lift yourself up or do much anymore. You could only lean against Nightmare and weakly grab at his hoodie to offer yourself some support as Nightmare manually lifted your body up and down, taking in the sweet pleasure of your limp frame and used body that was now his. You couldn't even tell what number this tentacle was, you just leaned on your 'mate' and allowed him to use your body the way he wanted. You were too tired to do much of anything, eyes drooping as you flowed in and out of consciousness.

With a final groan the tar-covered skeleton slipped the last tentacle out, a proud grin on his face as he stared at you with carnal hunger and desire "Now now, you have to stay up for the final course" he said with a sick grin as he pulled his shorts down enough to free his weeping length, it was engorged with ridges and a thick knot had grown at it's base. With ease he lifted your body before thrusting his length into you in one go, a horas moan escaped you at the sudden change of texture, his member wasn't smooth like his tentacles and dug into your magic, almost locking itself inside you had Nightmare forced his knot in. He hummed in content pleased to finally feel your soft walls around his girth, he wasted no time to dig into you, the ridges along his member rubbing your magic raw as they squeezed and clenched around him. A sudden sharp pain up your neck drew you out of your haze, your eyes widened in shock at the feeling of razor sharp teeth digging deep into your neck, Nightmare's cold magic seeping into your's as he claimed you. Hilting himself inside you, tying his knot before finally cumming, your stomach protested as it was filled with the tar-like magic with no way of releasing it as the knot ensured that nothing could seep out. 

The cold magic running through you made your vision hazy and your head spin, as if it were a sedative. Your sockets drooped shut as you lost consciousness, Nightmare's magic forcing your soul into a sleeping state as he combed through your 'hair' as if to help lull you to sleep, a wide grin spreading across his face as he watched his 'mate' fall unconscious.

**Author's Note:**

> Um, if y'all want me to make more chapters then please tell? I've been wanting to get back into writing ;w;


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